1. Field of Invention
This invention relates to rolls, such as for use in electrostatographic imaging devices.
2. Description of Related Art
Electrostatic reproduction involves uniformly charging a photoconductive member, or photoreceptor, and imagewise discharging it, or imagewise exposing it, based on light reflected from an original image being reproduced. The result is an electrostatically-formed latent image on the photoconductive member. The latent image is developed by bringing a charged developer material into contact with the photoconductive member.
Two-component and single-component developer materials are known. Two-component developer materials comprise magnetic carrier particles and charged toner particles that adhere triboelectrically to the carrier particles and are intended to adhere the photoconductive member.
A single-component developer material typically consists of only toner particles. The toner particles typically have an electrostatic charge to adhere to the photoconductive member, and magnetic properties to magnetically convey the toner particles from the sump to the magnetic roll. The toner particles adhere directly to the donor roll by electrostatic charges. The toner particles are attracted to the donor roll from a magnet or developer roll. From the donor roll, the toner is transferred to the photoconductive member in the development zone.
For both types of developer material, the charged toner particles are brought into contact with the latent image to form a toner image on the photoconductive member. The toner image is transferred to a receiver sheet, which passes through a fuser device where the toner particles are heated and permanently fused to the sheet, forming a hard copy of the original image.
A development device is used to bring the charged toner particles into contact with the latent image formed on the photoreceptor, so that the toner particles adhere electrostatically to the charged areas on the latent image. The development device typically includes a chamber in which the developer material is mixed and charged.
One type of two-component development method and apparatus is known as xe2x80x9cscavengeless development.xe2x80x9d In scavengeless development systems, toner is detached from the donor roll by applying an alternating current (AC) electric field to electrodes disposed between the donor roll and the photoconductive member. There is no physical contact between the development apparatus and the photoconductive member. Scavengeless development is useful in apparatus in which different types of toner are supplied to the same photoconductive member.
xe2x80x9cHybridxe2x80x9d scavengeless development apparatus typically includes a mixing chamber that holds a two-component developer material, a developer material developer or magnetic roll, a donor roll, a development zone, and an electrode structure at the development zone between the donor roll and the photoconductive member. The donor roll receives charged toner particles from the developer roll and transports the particles to the development zone. An AC voltage is applied to the electrodes to form a toner cloud in the development zone. Electrostatic fields generated by an adjacent latent image on the photoconductive member surface attract charged toner particles from the toner cloud to develop the latent image on the photoconductive member.
Another variation on scavengeless development uses single-component developer material development systems. As in two-component developer material development systems, the donor roll and electrodes also create a toner cloud.
In both one-component and two-component developer scavengeless development systems, the electrical, chemical and physical characteristics of the donor roll affect the ability of the development apparatus to effectively transport toner particles into the development zone and to achieve high-quality image development. The donor roll should have characteristics that enable charged toner particles to effectively and controllably adhere electrostatically to the donor roll""s outer surface, and be donated to the photoconductive member. It is desirable that the electrical properties of the donor roll be uniform and also tunable. It is also desirable that the donor roll be able to withstand wear and harmful chemicals.
The donor roll outer surface should also have sufficient mechanical properties, including wear resistance, to withstand wear and other types of degradation during service.
It is also desirable that the outer surface of the donor roll have a smooth finish (low roughness).
It is also desirable that the outer surface of the donor roll have good machining characteristics so that a desired surface finish can be formed.
It is also desirable that the outer surface of the donor roll comprises a material that is chemically resistant to withstand exposure to certain chemicals.
It is further also desirable that the outer surface of the donor roll comprises a material that has sufficient thermal properties.
It is still further desirable that the outer surface of the donor roll not be difficult to form and process.
This invention provides rolls, such as donor rolls, that comprise a glass coating that enables charged toner to effectively and controllably adhere electrostatically to the roll, and to be effectively donated to a photoconductive member to form an images.
This invention separately provides rolls having coatings that can be formed using conventional coating techniques.
This invention separately provides rolls having coatings with more uniform, and tunable, electrical properties.
This invention separately provides rolls having coatings with controlled mechanical properties.
This invention separately provides rolls having coatings with high hardness and wear resistance.
This invention separately provides rolls having an outer surface with a smooth finish.
This invention separately provides methods of making such rolls.
Exemplary embodiments of the rolls according to this invention comprise a core and a coating formed over the core. The coating comprises a glass material. Exemplary embodiments of the coating can also provide desired electrical, mechanical, chemical and/or thermal properties.
The properties of the coating make the rolls suitable for use in an electrostatographic imaging apparatus, such as for use in hybrid scavengeless development.
The coatings of the rolls can be applied onto substrates such as cores using conventional coating techniques. Further, the coatings can be processed using conventional finishing techniques.
Exemplary embodiments of the methods of forming the rolls according to this invention comprise applying a glass coating over a core. The coating can be applied over the core by any suitable glass coating process.